Vitamin B1 (Thiamin) Uses, Benefits, Side Effects & How to Take Supplements

Vitamin B1 was the first of eight vitamins in the “B Complex” to be discovered.

Also called thiamin (sometimes spelled thiamine), this vitamin is used in the body largely to convert carbohydrates into usable energy in the form of ATP (adenosine triphosphate).

Additionally, B1 is important for proper functioning of the brain, nervous system, and liver and for and maintaining the health of the eyes, skin, and hair.

Supplementing the diet with vitamin B1 is purported to have benefits for stress relief. There is some evidence that thiamine may strengthen the immune system and enhance the ability to resist cellular damage from stress. [2]

As a dietary supplement, it is also used to promote athletic performance, cognitive ability, weight loss, hangover relief, and for treatment of alcohol withdrawal symptoms. It has also been shown to prevent insect bites and is sometimes used as a mosquito repellent for humans and dogs.

This article will discuss how vitamin B1 works in the body, deficiency issues, health benefits, food sources, dosages, safety, and side effects.

Thiamine

Vitamin B1 Supplement

Energy

Brain Health

Well-Being

How It Works:

• Supports energy production
• Supports healthy nerve function
• Precursor to thiamin diphosphate for glucose metabolism

Dosage:

Between 100 - 500 mg per day

Safety:

Rated Likely Safe

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How does Vitamin B1 Work in the Body?

Vitamin B1 plays a critical role in the growth, development, maintenance and function of cells and is necessary for normal energy metabolism.

B vitamins are all water soluble or hydrophilic. Unlike fat soluble vitamins, they are not stored in fat cells inside the body. We must constantly replenish our supply of these nutrients by eating food sources that contain them. [1]

Although every living organism requires vitamin B1 to sustain life, not all organisms are capable of biosynthesizing it. Thiamine is only produced in some plants, bacteria, and fungi.

Thiamine is an essential nutrient for humans, meaning that we cannot produce it in our bodies. We have to obtain this vitamin by eating plants and animals that contain it or by taking a dietary supplement. [2]

Because this nutrient is required for converting glucose (sugar) into ATP (energy molecule), it is necessary for maintaining mitochondrial energy production inside the cells.

Nearly every cell in the body uses ATP as its primary fuel source to function. Without adequate thiamine in the body, certain carbohydrates and branched chain amino acids cannot be utilized to generate energy. This can hinder the efficiency of numerous biological processes.

According to the University of Maryland Medical Center (UMM) all B complex vitamins are required for important functions of the endocrine, digestive, and cardiovascular systems.

Vitamin B1 Deficiency

According to the UMM, vitamin B1 deficiency is rare in developed countries because the average diet contains a diverse assortment of foods. Vitamin fortification of foods is also common. [1]

People in developing countries are more at risk of developing symptoms of deficiency, especially when the diet mostly consists of processed white rice.

In Japan, deficiencies in this vitamin were very common when processed rice products were first introduced. Nutrient enrichment programs have since improved rates of deficiency in this country.

Those most likely to develop vitamin B1 deficiency include severe alcoholics and people undergoing kidney dialysis. People who have health conditions that disrupt intestinal absorption of nutrients are also at risk, including individuals diagnosed with anorexia and/or have Crohn’s disease.

Some of the most common symptoms associated with vitamin B1 deficiency include:

• Nausea
• Irritability
• Abdominal Pain
• Headache
• Fatigue
• Depression

Chronically low levels can also cause nerve damage, muscle weakness, heart problems, memory loss, weight loss, and/or psychosis.

A severe and chronic form of Vitamin B1 deficiency is known as beriberi. The condition is subdivided into four categories: dry beriberi, wet beriberi, infantile beriberi, and gastrointestinal beriberi.

• Dry Beriberi
• Wet Beriberi
• Infantile Beriberi
• Gastrointestinal Beriberi

Dry beriberi affects the peripheral nervous system. It can cause muscle wasting, partial paralysis, difficulty walking, loss of lower leg function, and mental confusion.

Severe thiamine deficiency can cause a brain disorder called Wernicke-Korsakoff syndrome, which is considered a form of dry beriberi. This syndrome is marked by two separate conditions: peripheral neuropathy (nerve damage) and memory loss.

Wet beriberi affects the cardiovascular system. Symptoms often include increased heart rate, shortness of breath, and peripheral edemas (swelling of the lower legs caused by fluid build-up). Wet beriberi is sometimes fatal as it can cause heart failure.

Gastrointestinal beriberi affects the gastrointestinal system and causes abdominal pain, nausea, and vomiting.

Infantile beriberi can occur in infants whose mothers breastfeed and have inadequate thiamine intake. The deficiency is passed on to the infant through breastmilk and can cause developmental issues.

Vitamin B1 Health Benefits

The NMCD states that vitamin B1 supplements are used for a variety of reasons including: [2]

• Anti-aging
• Boosting the immune system
• Cervical cancer
• Chronic diarrhea and other gastrointestinal disorders
• Enhancing learning abilities
• Heart disease
• Improving athletic performance
• Inhibiting West Nile virus
• Mood enhancement
• Neuritis (nerve inflammation) associated with pregnancy and pellagra
• Prediabetes
• Reducing stress

According to NMCD, this supplement is also used for treating and/or preventing alcoholism, motion sickness, poor appetite, and canker sores.

The NMCD rates Vitamin B1 as Effective for the following uses:

• Treating thiamin deficiency
• Wernicke-Korsakoff syndrome
• Certain rare metabolic conditions
• Subacute necrotizing encephalopathy (SNE, Leigh’s disease)
• Maple syrup urine disease (branched-chain aminoacidopathy)
• Lactic acidosis associated with pyruvate carboxylase deficiency and hyperalaninemia [2]

The NMCD also rates this vitamin as Possibly Effective for cataracts, diabetic neuropathy, and dysmenorrhea.

There have been some promising results from clinical trials using thiamine for other purposes, however this research is limited. More clinical research is still needed to determine the therapeutic efficacy of thiamine for these uses.

Injectable vitamin B1 is a FDA-approved prescription drug. All other formulations of thiamine are considered dietary supplements which have not been approved by the FDA to prevent or treat any medical conditions.

Wernicke-Korsakoff Syndrome

According to the Natural Medicines Comprehensive Database (NMCD) one of the most common uses for vitamin B1 is to treat beriberi and/or Wernicke-Korsakoff syndrome caused by severe thiamine deficiency.

NMCD states that high doses of this vitamin will likely help the confusion and incoordination that are often associated with Wernicke-Korsakoff syndrome. However, it does not often seem to improve the symptom of memory loss.

Alzheimer’s Disease

Low levels of thiamine in the body can cause dementia in those with Wernicke-Korsakoff syndrome.

Because of this, researchers hypothesize that it may help to improve cognitive decline disorders like Alzheimer’s disease in people without deficiencies.

In some trials oral vitamin B1 supplementation has been shown to cause some improvements to cognitive function in Alzheimer’s patients. [3] However, many elderly people develop poor thiamine absorption problems, which may limit success.

Research is ongoing to determine how vitamin absorption in the elderly may be improved, possibly opening a novel method for treating cognitive decline in Alzheimer’s and related conditions.

More research is still needed to determine if and how vitamin B1 affects Alzheimer’s disease or any other conditions that cause cognitive decline.

Thiamine has not been approved by the FDA as a drug for treating or preventing Alzheimer’s disease and other cognitive decline conditions.

Myocardial Infarction

Myocardial infarction is another term used for heart attack. Many doctors prescribe diuretic medications for patients that have had heart failure.

Diuretic medications increase diuresis (urine production) in the kidneys. They also increase the volume and frequency of urination.

Because diuretics increase the amount of fluids excreted via urination, there is some concern that diuretics can decrease the amount of thiamine and other important nutrients in the body.

They may cause these vitamins to be flushed out of the body faster, resulting in potential deficiency even among people who obtain enough from their diet.

Some small studies have suggested that taking a vitamin B1 supplement may help to decrease the risk of deficiency in those using diuretics medications for myocardial infarction.

More research is needed to determine whether this supplement might have health benefits fpr those using diuretics for heart failure or any health conditions.

Cataracts

The lens of the eye is a body part that can be particularly sensitive to nutrient deficiencies. Some preliminary evidence suggests that higher intake of vitamin B1 might help to lower the risk of developing cataracts, especially with high intake of other vitamins.

Population based research has shown that people with higher intake of certain vitamins are less likely to develop cataracts and certain other eye/vision disorders than people with lower intake of these nutrients. [2]

A correlation has been established between intake of vitamins A (retinol), B1, B2 (riboflavin), B3 (niacin), B9 (folate), B12 (cyanocobalamin), C (ascorbic acid), and E (alpha-tocopherol) and eye health.

At this time not enough research has been completed yet to determine how these or other nutrients directly affect the development of cataracts or other eye/vision problems.

More research is still needed to determine the effects of vitamin B1 on cataracts and eye health in general.

Best Vitamin B1 Food Sources

According to Dieticians of Canada and the U.S. National Institutes of Health, the following are some of the best food sources for vitamin B1: [5, 6]

• 1/4 cup shelled sunflower seeds: 0.54 mg
• 1/4 cup raw wheat germ: 0.5 mg
• 3 oz bone in pork chop: 0.4 mg
• 3 oz dry heat cooked trout: 0.4 mg
• 1/2 cup boiled black beans: 0.4 mg
• 1.2 cup cooked edamame: 0.25 mg
• 1/2 cup baked acorn squash: 0.2 mg
• 1 cup whole wheat cooked pasta: 0.2 mg

Vitamin B1 can be found in large amounts in most types of animal meats and organs including pork, beef, poultry, bison, rabbit, and venison.

There are various other good sources including spinach and other green leafy vegetables, yeast, certain nuts and grains, certain beans and legumes, and blackstrap molasses.

Many breads, pastas, and cereals are also fortified with B vitamins including thiamin. One serving of fortified breakfast cereal often provides nearly the day’s entire requirement for this vitamin.

Whenever available and possible, it is recommended to try and obtain necessary nutrients from food sources. If this is not possible, then taking a high-quality Vitamin B1 supplement or a B complex multivitamin may be useful.

Types of Vitamin B1 Supplements

The University of Maryland Medical Center states that thiamine supplements are available commonly in capsule, tablet, and lozenge forms. Vitamin B1 is commonly listed on supplement labels as either thiamine hydrochloride or thiamine mononitrate.

Thiamine as a single ingredient is available in a few different dosages, most commonly as 100 mg doses, although 50 mg, 300 mg, and 500 mg formulations are also available. When it is included in a B-complex multivitamin, this vitamin is typically provided at amounts between 25-50 mg per dose.

The NMCD states that there are more than 7500 dietary supplement products available with vitamin B1 as either a sole or secondary ingredient. This means that there is a large variety of products to choose from, but also differing levels of quality.

Many supplements use petroleum products in their manufacturing processes. Some others do not use quality raw materials or do not conduct the required amount of ingredient testing.

When possible, look for vitamin B1 and other supplements that have been sourced from organic, non-GMO plant sources. It is recommended to try and choose high-quality supplements that are free of artificial additives, colors, preservatives, fillers, and flavors.

Unless otherwise instructed by your doctor, it is always recommended to follow the usage instructions on the label of any thiamine supplement you may use.

Vitamin B1 Dosage Recommendations

The Recommended Dietary Allowance (RDA) for this vitamin varies depending on age and health status.

In general, the RDA is the average daily consumption level for a specific nutrient that is sufficient to meet needs of nearly all healthy people ((97%-98% of the population).

The following RDA amounts are reported by the Mayo Clinic for Vitamin B1:

• Infants 0 to 6 months: 0.2 mg/day
• Infants 7 to 12 months: 0.3 mg/day
• Children 1 to 3 years: 0.5 mg/day
• Children 4 to 8 years: 0.6 mg/day
• Children 9 to 13 years: 0.9 mg/day
• Males 14 to 18 years: 1.2 mg/day
• Females 14 to 18 years: 1 mg/day
• Men 19 years of age and older: 1.2 milligrams (mg) per day
• Women 19 and older: 1.1 mg/day
• Pregnant or breastfeeding females of any age: 1.4 mg/day [4]

When used as a dietary supplement, dosages are typically much higher than the RDA values. The most common supplements provide 100 mg of thiamine as a single ingredient. Vitamin B1 is often included in slightly lower amounts in B-complex multivitamins, typically around 25-50 mg.

The National Academy of Medicine (formerly the Institute of Medicine) reports that no Tolerable Upper Intake Level (UL) has been set for humans. This means consuming higher than this amount is likely to be well-tolerated.

They also say that, “there are no reports available of adverse effects from consumption of excess thiamin by ingestion of food and supplements.” [7]

Dosages used in research studies have varied depending on the purpose. Some dosages used in clinical trials include: [2]

• 5-30 mg per day for a month for thiamin deficiency
• 10 mg per day for cataracts
• 10-20 mg per day for metabolic disorders
• 100 mg per day for dysmenorrhea
• 100 mg three times per day for diabetic neuropathy
• 100 mg three times per day for prediabetes
• Up to 300 mg per day for severe deficiency

It is recommended that you seek medical advice about the best dose of vitamin B1 for your needs to help avoid side effects.

Vitamin B1 Side Effects

The NMCD rates vitamin B1 as Likely Safe when used orally and appropriately. It is also rated Likely Safe when used intravenously or intramuscularly when administered by a doctor.

Injectable Vitamin B1 is an FDA-approved prescription drug used to treat thiamine deficiency .

Vitamin B1 is generally well tolerated, although very rare cases of hypersensitivity, allergic reactions, and dermatitis have been observed. The UMM states that very high doses may cause stomach upset.

Chronic supplementation of one B-complex vitamin without balanced supplementation of the others is typically not recommended. Doing so may disrupt the levels of the other nutrients, possibly causing adverse outcomes for health.

It is often recommended to supplement vitamin B1 only as part of a complete B-complex multivitamin supplement unless otherwise recommended by your doctor.

Parenteral Administration of Vitamin B1

According to Nursing Times, parenteral administration of a drug refers to any non-oral administration, and typically refers to injections. Common parenteral drug administration routes are intramuscular, intravenous, and subcutaneous.

The NMCD says that there are some possible side effects of parenteral vitamin B1 administration. Some of these include tingling, pain, weakness, nausea, restlessness, respiratory distress, and pulmonary edema.

Some other rare adverse effects include gastrointestinal bleeding, tightness in the throat, low blood pressure (hypotension), vascular collapse, and in severe cases, death.

Vitamin B1 is FDA-approved as an injectable pharmaceutical. In this format this product is only to be used by doctors in clinical environments.

Vitamin B1 Drug Interactions

Vitamin B1 may interact with certain drugs, herbs, dietary supplement, nutrients, foods, health conditions, and laboratory tests.

Some types of drugs that might deplete or otherwise interact with thiamine include diuretics, contraceptives, and antibiotics.

Use caution if combining this supplement with fluorouracil (Adrucil), metformin (Glucophage), and/or phenytoin (Dilantin). [2]

Fluorouracil

Administration of chemotherapy agents that contain fluorouracil might increase the risk of developing vitamin B1 deficiency. It seems to affect thiamine activation, as well as upregulate its metabolic breakdown.

There have been some reports of vitamin B1 deficiency associated with administration of certain other chemotherapies, but researchers believe those are largely due to reduced appetite and subsequent nutrient intake issues.

Ask your oncologist about using supplements with any type of chemotherapy you may be receiving.

Metformin

Known by the brand name Glucophage, metformin is a popularly prescribed antidiabetic drug used to help manage the symptoms of diabetes mellitus. In theory, metformin can reduce the activities of vitamin B1 in the body.

Thiamine helps glycolytic pyruvate enter into Krebs cycle reactions, contributing to the production of adenosine triphosphate (ATP). Metformin may act to reduce thiamin actions, subsequently causing more pyruvate to be converted into lactic acid.

Researchers believe that this may result in lactic acidosis, which is common with metformin usage. These effects are theoretical and have not been explored in human subjects to date.

You should discuss using vitamin B1 supplements with your endocrinologist if you have diabetes or prediabetes (metabolic syndrome).

Phenytoin

Sold under the name Dilantin, phenytoin is an anticonvulsant drug prescribed to prevent or treat seizures. Preliminary evidence suggests that phenytoin can reduce the amount of thiamine in both cerebrospinal fluid and plasma.

Researchers think this effect might be caused by phenytoin inhibiting uptake of thiamine into nervous tissues.

In theory, this could result in conditions marked by involuntary body movements, possibly developing into cerebellar ataxia (damage of the cerebellum causing movement disorders) or polyneuropathy (peripheral nerve degeneration).

Supplement & Food Interactions & Contraindications

Certain polyphenol tannins in coffee and tea can convert vitamin B1 into an unusable form. This is not normally an issue as long as there is adequate thiamine and ascorbic acid (vitamin C) in the diet.

Raw freshwater fish and some shellfish contain thiaminase enzymes which destroy this vitamin.

Those who consume higher than average amounts of raw seafoods may be at higher risk for developing thiamine deficiency. Cooking these foods inhibits the enzymes that destroy vitamin B1.

Alcoholism is often associated with vitamin B1 deficiency. According to the NMCD, alcoholics commonly have low thiamine levels because of poor diet and/or impaired ability to absorb available nutrients.

Low vitamin B1 levels also seem to worsen nerve damage associated with alcoholism. This supplement will sometimes be used in patients undergoing alcohol withdrawal.

People undergoing hemodialysis and those taking diuretic medications are at higher risk for developing vitamin B1 deficiency. According to the NMCD taking a thiamine supplement is frequently advised in these groups.

Betel nuts (areca nuts) can reduce the biological activities of thiamine. Those who regularly eat these nuts over time are more likely to develop deficiency.

Supplementation may affect the result of Schack and Waxler spectrophotometric testing of serum theophylline levels.

Thiamine can also cause false positive results in tests for determining the presence of uric acid.

As with all nutrients and dietary supplements, it is best to discuss using vitamin B1 supplements with a qualified medical professional before beginning use. This is especially true if you use any prescription medications or if you have any type of pre-existing health condition.

Talk about your health and the medicines you use with your doctor before starting to supplement your diet with additional vitamin B1.

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